The Surefire F 27 blue filter is useful for tracking game or trying to read a map in the dark. This filter produces a smooth beam of blue light that benefits hunters when tracking wounded game at night by making blood stand out more distinctly against foliage. For close range, non-tactical use, the blue filter reduces the intensity of light output. This filter fits all flashlights with a 1.25-inch bezel, flips up to allow instant access to the normal beam of light, and adds protection for the flashlight lens.